The American poster format (the famous 24 × 36 inches, or 61x91 cm in French) is a more vertical format than the traditional French poster formats (120x160 cm).
That's good, because Parasite is also a more vertical film than the others. And the poster of Marie Bergeron perfectly illustrates to us this idea that the wealth of the upper classes is due to a precarious balance, threatened by the desires of ascension of the most disadvantaged.